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The injectors you buy might depend on what platform you're starting with. The cars and trucks generally use different injector bodies and seats, and different electrical connectors. I'm building an L33 that came as a full drop-out with harness and ECU, and didn't want to change the electrical connectors for my injectors, or use small, pre-wired adapters.

A bit of research seemed to indicate that the truck flex fuel injectors are about a 33 lb injector and my OE injectors were about 24 lbs. I have a set for my swap now, but everything is still in a huge pile of boxes on the floor, so no results yet.

Your tuner is probably looking at the injector duty cycle. If you're getting values over 80% you should go bigger. My injectors are 22 lb (measured at the usual standard 43.5 psi) but I don't know the duty cycle they reach in my engine. On the dyno my mixture looks good at peak power.

Going to stick with the 36lb injectors I am running. Tuner wants me to bump it up to 42lb injectors but I'm really happy with how the car is running.

what sort of power are you putting down?

ill second that guess that your hitting more than 80% dc. if thats the case, if you should upgrade or not depends on a few factors. is the car just for the street, or is it a track car, and does it spend a lot of time at higher rpm?

the whole thought is above 80% duty cycle the injector will start getting hot, and at higher duty cycles fuel control isnt as accurate. on a street car its not as big a concern if your 85-90% duty cycle at peak power because you may hit that for a few seconds and then it drops again. however, in a track car it could be an issue. if your tearing down a long straight your at wide open throttle and near peak power for quite a long time, the high duty cycle can cause the injector to overheat, burn out the coil or stick the pintle.

myself, i have no problem with 90% duty cycle on the street. my cobalt ss from factory hit 97% duty cycle at peak power, dead stock. its quite common for them. if it caused damage gm would have had larger injectors from factory. flip side is the gm stage 1 upgrade kit consists of a large set of injectors and a reflash and you gain 25hp.

it going lean could be caused by 3 factors. first, could be the tune, although id rule that out being the tuner recognizes it and wants you to upgrade. second, could be the fuel pump, it may be too small of a pump and causing the lean condition. ive seen many times where people try to mask a fuel pump problem by putting bigger injectors in. its an easy to test, toss a fuel pressure gauge on the rail and stick it on the hood and go for a burn, see what it does. the 3rd thing, if the pump is good, then the injectors are maxed and need upgrading.

if the car is going lean thats a problem that needs to be addressed. my last post about injector duty cycle is only relevent for an engine that isnt going lean.

wanczykj wrote:The car isn't running lean all the time, just at the top end when you are wide open throttle.

That may be where you discovered the lean condition but that isn’t accurate. Lean conditions aren’t sensitive to RPM or throttle position it’s sensitive to load. When a fuel system can’t keep up with an engine’s demand it goes lean. During lean conditions, combustion temperatures go stupid high and the pistons can literally melt to the cylinder walls. This happens to drag cars all the time in just a few seconds. A street car is just as likely to go lean in 5th gear on moderate grades at moderate speeds and low/moderate RPMs (high load).

I agree with Doc, a set of injectors isn’t worth betting your engine on.